Novel Peroxide Curable Butyl Rubber with Fillers

        Butyl elastomer, a copolymer of isobutylene with small amounts of isoprene (~2 mole %), is the most important rubber manufactured commercially via carbocationic polymerization.  Subsequently, halogenated butyl rubber was developed to increase the crosslinking reactivity and co-compatibility of butyl rubber with other highly unsaturated elastomers.  Traditionally, sulfur, zinc species, resins or amines were used to crosslink regular and halogenated butyl rubber to make practical consumer end-products (e.g. tires) and it was widely believed that regular butyl rubber could not undergo peroxide crosslinking.

       LANXESS has developed a new technology to produce butyl elastomers containing up to 8 mole % of isoprene.  Due to the increased isoprene level in the butyl rubber, in addition to sulfur and zinc species, compounders can now use peroxides as a means to cure regular butyl rubber.  The use of peroxides as a crosslinking agent expands the potential consumer product range for butyl rubber.  Results highlighting the use of a design of experiment (DOE) to tailor the levels of peroxide and co-agent to obtain the desired properties of the cured elastomeric materials will be presented.  Special focus will be given to black-filled rubber compounds.